Chemical deposition has been known to be a slow deposition process. Moreover, the process has been recognized to be generally inefficient. For example, when a pattern of metal deposit is to be chemically formed on a substrate as practiced in the manufacture of electronic circuit devices, masking has been commonly required and is quite often highly intricate. Not only does the conventional masking procedure make the total process inefficient and costly, it imposes serious restriction on the size of the pattern which can be batch-deposited.
With the chemical deposition process, difficulties have also been encountered in assuring uniformity of a layer of deposit, especially where the receiving substrate is shaped with an intricate contour having ridges or edges and recesses. Generally, the deposit tends to build up predominantly on relatively projecting areas and may occur hardly at all at a recessed corner portion, resulting in an irregularity of deposition over the entire surface and this tendency is generally accentuated as the process continues. While various techniques have been proposed to reduce the deposit irregularity, none of them has been found to be satisfactory on account of efficiency and economy.
In general, there is a consistent desire in the art of chemical or electroless deposition to increase the rate of deposition, to enhance the efficiency of the process and to develop a high-precision layer of deposit which is uniform or controllable in thickness.